EP2988445A1

EP2988445A1 - Method for processing dropped frames and decoder

Info

Publication number: EP2988445A1
Application number: EP14825749.6A
Authority: EP
Inventors: Bin Wang; Lei Miao; Zexin Liu
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2013-07-16
Filing date: 2014-01-07
Publication date: 2016-02-24
Anticipated expiration: 2034-01-07
Also published as: EP2988445B1; WO2015007076A1; CN104301064B; CN108364657B; EP4350694A2; EP3595211B1; US10614817B2; EP4350694A3; CN104301064A; CN108364657A; ES2738885T3; EP3595211A1; EP2988445A4; KR101807683B1; DE202014011512U1; JP2016529542A; KR20160005069A; JP6264673B2; ES2980990T3; US20160118054A1

Abstract

Embodiments of the present invention provide a method for processing a lost frame, and a decoder. The method includes: determining a synthesized high frequency band signal of a current lost frame; determining recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame; determining a global gain gradient of the current lost frame according to the recovery information; determining a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame; and adjusting the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and a subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame. The embodiments of the present invention enable transition of a high frequency band signal of a current lost frame to be natural and smooth, and can attenuate noise in the high frequency band signal, thereby improving quality of the high frequency band signal.

Description

This application claims priority to Chinese Patent Application No. 201310297740.1, filed with the Chinese Patent Office on July 16, 2013 , and entitled "METHOD FOR PROCESSING LOST FRAME, AND DECODER", which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to the field of communications, and in particular, to a method for processing a lost frame, and a decoder.

BACKGROUND

With continuous progress of technologies, a user has an increasingly high requirement on speech quality. Increasing speech bandwidth is a main method for improving speech quality. If information about added bandwidth is coded in a conventional coding manner, a bit rate is greatly increased. In this case, a purpose of transmission cannot be achieved due to a limitation of current network bandwidth. Therefore, a bandwidth extension technology is often used to increase the bandwidth.
After coding a high frequency band signal by using the bandwidth extension technology, an encoder side transmits the coded signal to a decoder side. The decoder side also recovers the high frequency band signal by using the bandwidth extension technology. During signal transmission, due to network congestion or a fault or for other reasons, frame loss may be caused. Because a packet loss rate is a key factor that affects signal quality, to recover a lost frame as correctly as possible in a case of frame loss, a frame loss processing technology is proposed. In this technology, the decoder side may use a synthesized high frequency band signal of a previous frame as a synthesized high frequency band signal of the lost frame, and then adjust the synthesized high frequency band signal by using a subframe gain and a global gain of the current lost frame, to obtain a final high frequency band signal. However, in this technology, the subframe gain of the current lost frame is a fixed value, and the global gain of the current lost frame is obtained by multiplying a global gain of the previous frame by a fixed gradient, which causes discontinuous transition of the re-established high frequency band signal before and after the frame loss, and generation of severe noise in the re-established high frequency band signal.

SUMMARY

Embodiments of the present invention provide a method for processing a lost frame, and a decoder, which can improve quality of a high frequency band signal.
According to a first aspect, a method for processing a lost frame is provided, where the method includes: determining a synthesized high frequency band signal of a current lost frame; determining recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame; determining a global gain gradient of the current lost frame according to the recovery information; determining a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, where M is a positive integer; and adjusting the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and a subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
With reference to the first aspect, in a first possible implementation manner, the determining a global gain gradient of the current lost frame according to the recovery information includes: in a case in which it is determined that a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which it is determined that a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, determining that the global gain gradient is 1.
With reference to the first aspect, in a second possible implementation manner, the determining a global gain gradient of the current lost frame according to the recovery information includes: in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, determining the global gain gradient, and enabling the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
With reference to the first aspect, in a third possible implementation manner, the determining a global gain gradient of the current lost frame according to the recovery information includes: in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, or in a case in which it is determined that the last frame received before the frame loss is an audio frame or a silence frame, determining the global gain gradient, and enabling the global gain gradient to be greater than a preset first threshold.
With reference to the first aspect, in a fourth possible implementation manner, the determining a global gain gradient of the current lost frame according to the recovery information includes: in a case in which it is determined that the last frame received before the frame loss is an onset frame of an unvoiced frame, determining the global gain gradient, and enabling the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
With reference to the first aspect or any implementation manner of the first possible implementation manner to the fourth possible implementation manner of the first aspect, in a fifth possible implementation manner, the determining a subframe gain of the current lost frame includes: determining a subframe gain gradient of the current lost frame according to the recovery information; and determining the subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer.
With reference to the fifth possible implementation manner of the first aspect, in a sixth possible implementation manner, the determining a subframe gain gradient of the current lost frame according to the recovery information includes: in a case in which it cannot be determined whether the coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss or whether the frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determining the subframe gain gradient, and enabling the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
With reference to the fifth possible implementation manner of the first aspect, in a seventh possible implementation manner, the determining a subframe gain gradient of the current lost frame according to the recovery information includes: in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, determining the subframe gain gradient, and enabling the subframe gain gradient to be greater than a preset second threshold.
According to a second aspect, a method for processing a lost frame is provided, where the method includes: determining a synthesized high frequency band signal of a current lost frame; determining recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame; determining a subframe gain gradient of the current lost frame according to the recovery information; determining a subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer; and adjusting the synthesized high frequency band signal of the current lost frame according to the subframe gain of the current lost frame and a global gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
With reference to the second aspect, in a first possible implementation manner, the determining a subframe gain gradient of the current lost frame according to the recovery information includes: in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determining the subframe gain gradient, and enabling the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
With reference to the second aspect, in a second possible implementation manner, the determining a subframe gain gradient of the current lost frame according to the recovery information includes: in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, determining the subframe gain gradient, and enabling the subframe gain gradient to be greater than a preset second threshold.
According to a third aspect, a decoder is provided, where the decoder includes: a first determining unit, configured to determine a synthesized high frequency band signal of a current lost frame; a second determining unit, configured to determine recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame; a third determining unit, configured to determine a global gain gradient of the current lost frame according to the recovery information; a fourth determining unit, configured to determine a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, where M is a positive integer; and an adjusting unit, configured to adjust the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and a subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
With reference to the third aspect, in a first possible implementation manner, the second determining unit is specifically configured to: in a case in which it is determined that a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which it is determined that a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, determine that the global gain gradient is 1.
With reference to the third aspect, in a second possible implementation manner, the second determining unit is specifically configured to: in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
With reference to the third aspect, in a third possible implementation manner, the second determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, or in a case in which it is determined that the last frame received before the frame loss is an audio frame or a silence frame, determine the global gain gradient, and enable the global gain gradient to be greater than a preset first threshold.
With reference to the third aspect, in a fourth possible implementation manner, the second determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of an unvoiced frame, determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
With reference to the third aspect or any implementation manner of the first possible implementation manner to the fourth possible implementation manner of the third aspect, in a fifth possible implementation manner, the decoder further includes: a fifth determining unit, configured to determine a subframe gain gradient of the current lost frame according to the recovery information, and determine the subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer.
With reference to the fifth possible implementation manner of the third aspect, in a sixth possible implementation manner, the fifth determining unit is specifically configured to: in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss or whether the frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
With reference to the fifth possible implementation manner of the third aspect, in a seventh possible implementation manner, the fifth determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of an unvoiced frame, determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
According to a fourth aspect, a decoder is provided, where the decoder includes: a first determining unit, configured to determine a synthesized high frequency band signal of a current lost frame; a second determining unit, configured to determine recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame; a third determining unit, configured to determine a subframe gain gradient of the current lost frame according to the recovery information; a fourth determining unit, configured to determine a subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer; and an adjusting unit, configured to adjust the synthesized high frequency band signal of the current lost frame according to the subframe gain of the current lost frame and a global gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
With reference to the fourth aspect, in a first possible implementation manner, the second determining unit is specifically configured to: in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a second threshold and greater than 0.
With reference to the fourth aspect, in a second possible implementation manner, the second determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a second threshold.
In the embodiments of the present invention, a global gain gradient of a current lost frame is determined according to recovery information, a global gain of the current lost frame is determined according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the global gain of the current lost frame and a subframe gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments of the present invention. Apparently, the accompanying drawings in the following description show merely some embodiments of the present invention, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.

FIG. 1 is a schematic flowchart of a method for processing a lost frame according to an embodiment of the present invention;
FIG. 2 is a schematic flowchart of a method for processing a lost frame according to another embodiment of the present invention;
FIG. 3 is a schematic flowchart of a process of a method for processing a lost frame according to an embodiment of the present invention;
FIG. 4 is a schematic block diagram of a decoder according to an embodiment of the present invention;
FIG. 5 is a schematic block diagram of a decoder according to another embodiment of the present invention;
FIG. 6 is a schematic block diagram of a decoder according to an embodiment of the present invention; and
FIG. 7 is a schematic block diagram of a decoder according to another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
Coding technologies and decoding technologies are widely applied in various electronic devices, for example, a mobile phone, a wireless apparatus, a personal data assistant (Personal Data Assistant, PDA), a handheld or portable computer, a global positioning system (Global Positioning System, GPS) receiver/navigator, a camera, an audio/video player, a video camera, a video recorder, and a monitoring device.
To increase speech bandwidth, a bandwidth extension technology is often used. Specifically, an encoder side may code low frequency band information by using a core-layer encoder, and perform linear predictive coding (Linear Predictive Coding, LPC) analysis on a high frequency band signal, to obtain a high frequency band LPC coefficient. Then, a high frequency band excitation signal is obtained according to parameters such as a pitch period, an algebraic codebook, and gains that are obtained by the core-layer encoder. After the high frequency band excitation signal is processed by an LPC synthesis filter that is obtained by using an LPC parameter, a synthesized high frequency band signal is obtained. By comparing the original high frequency band signal with the synthesized high frequency band signal, a subframe gain and a global gain are obtained. The foregoing LPC coefficient is converted into an LSF parameter, and the LSF parameter, the subframe gain, and the global gain are quantized and coded. Finally, a bitstream obtained by means of coding is sent to a decoder side.
After receiving the coded bitstream, the decoder side may first parse information about the bitstream to determine whether any frame is lost. If frame loss does not occur, the bitstream may be normally decoded; or if frame loss occurs, the decoder side may process a lost frame. A method for processing a lost frame by a decoder side is described in detail below with reference to the embodiments of the present invention.
FIG. 1 is a schematic flowchart of a method for processing a lost frame according to an embodiment of the present invention. The method in FIG. 1 is executed by a decoder side.
110: Determine a synthesized high frequency band signal of a current lost frame.
For example, the decoder side may determine a synthesized high frequency band excitation signal of the current lost frame according to a parameter of a previous frame of the current lost frame. Specifically, the decoder side may use an LPC parameter of the previous frame of the current lost frame as an LPC parameter of the current frame, and may obtain a high frequency band excitation signal by using parameters such as a pitch period, an algebraic codebook, and gains that are obtained by a core-layer decoder of the previous frame. The decoder side may use the high frequency band excitation signal as a high frequency band excitation signal of the current lost frame, and then process the high frequency band excitation signal by using an LPC synthesis filter that is generated by using the LPC parameter, to obtain the synthesized high frequency band signal of the current lost frame.
120: Determine recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame.
The current lost frame may refer to a lost frame that needs to be processed by the decoder side currently.
The coding mode before the frame loss may refer to a coding mode before occurrence of a current frame loss event. Generally, to achieve better coding performance, an encoder side may classify signals before coding the signals, to select a suitable coding mode. At present, the coding mode may include: a silence frame coding mode (INACTIVE mode), an unvoiced frame coding mode (UNVOICED mode), a voiced frame coding mode (VOICED mode), a generic frame coding mode (GENERIC mode), a transition frame coding mode (TRANSITION mode), and an audio frame coding mode (AUDIO mode).
The frame class of the last frame received before the frame loss may refer to a frame class of a last frame that is received by the decoder side before occurrence of the current frame loss event. For example, it is assumed that the encoder side sends four frames to the decoder side, and the decoder side correctly receives the first frame and the second frame while the third frame and the fourth frame are lost; then, the last frame received before the frame loss may refer to the second frame. Generally, a frame class of a frame may include: (1) a frame (UNVOICED_CLAS frame) that has any one of the following features: unvoiced, silence, noise, and voiced ending; (2) a frame (UNVOICED_TRANSITION frame) of transition from an unvoiced sound to a voiced sound, where the voiced sound is on the onset but is still relatively weak; (3) a frame (VOICED_TRANSITION frame) of transition after a voiced sound, where a feature of the voice sound is already very weak; (4) a frame (VOICED_CLAS frame) that has a feature of a voiced sound, where a previous frame of this frame is a voiced frame or a voiced onset frame; (5) an onset frame (ONSET frame) with an obvious voiced sound; (6) an onset frame (SIN_ONSET frame) with mixed harmonic and noise; and (7) a frame (INACTIVE_CLAS frame) with an inactive feature.
The quantity of continuously lost frames may refer to the quantity of frames that are continuously lost until the current lost frame in the current frame loss event. In essence, the quantity of continuously lost frames may indicate a ranking of the current lost frame in the continuously lost frames. For example, the encoder side sends five frames to the decoder side, the decoder side correctly receives the first frame and the second frame, and the third frame to the fifth frame are all lost. If the current lost frame is the fourth frame, the quantity of continuously lost frames is 2; or if the current lost frame is the fifth frame, the quantity of continuously lost frames is 3.
130: Determine a global gain gradient of the current lost frame according to the recovery information.
140: Determine a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, where M is a positive integer.
For example, the decoder side may weight global gains of the previous M frames, and then determine the global gain of the current lost frame according to the weighted global gains and the global gain gradient.
Specifically, a global gain FramGain of the current lost frame may be represented by using an equation (1): $FramGain = f (α, FramGain (- m))$
where
FramGain(-m) may represent a global gain of the m^th frame in the previous M frames, and α may represent the global gain gradient of the current lost frame.
For example, the decoder side may determine a global gain FramGain of the current lost frame according to the following equation (2): $FramGain = α * \sum_{m = 1}^{M} w_{n} FramGain (- m)$
$\sum_{m - 1}^{M} w_{n} = 1$
wm may represent a weighted value that corresponds to the m^th frame in the previous M frames, FramGain(-m) may represent a global gain of the m^th frame, and α may represent the global gain gradient of the current lost frame.
It should be understood that the example of the foregoing equation (2) only aims to help a person skilled in the art better understand this embodiment of the present invention, but is not intended to limit the scope of this embodiment of the present invention. The person skilled in the art may make various equivalent modifications or changes based on the equation (1), to determine various specific representation forms of the equation (1), where these modifications or changes also fall within the scope of the present invention.
Generally, to simplify a process of step 130, the decoder side may determine the global gain of the current lost frame according to a global gain of the previous frame of the current lost frame and the global gain gradient.
150: Adjust the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and a subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
For example, the decoder side may set the subframe gain of the current lost frame to a fixed value, or the decoder side may determine the subframe gain of the current lost frame in a manner to be described below. Then, the decoder side may adjust the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and the subframe gain of the current lost frame, thereby obtaining the final high frequency band signal.
In the prior art, the global gain gradient of the current lost frame is a fixed value, and the decoder side obtains the global gain of the current lost frame according to the global gain of the previous frame and the fixed global gain gradient. The adjusting the synthesized high frequency band signal according to the global gain of the current lost frame that is obtained by using this method may cause discontinuous transition of the final high frequency band signal before and after the frame loss, and generation of severe noise. However, in this embodiment of the present invention, the decoder side may determine the global gain gradient according to the recovery information, instead of simply setting the global gain gradient to a fixed value. The recovery information describes a related feature of the frame loss event, and therefore, the global gain gradient determined according to the recovery information is more accurate, so that the global gain of the current lost frame is also more accurate. Therefore, the decoder side adjusts the synthesized high frequency signal according to the global gain, so that transition of the re-established high frequency band signal can be natural and smooth, and the noise in the re-established high frequency band signal can be attenuated, thereby improving quality of the re-established high frequency band signal.
In this embodiment of the present invention, a global gain gradient of a current lost frame is determined according to recovery information, a global gain of the current lost frame is determined according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the global gain of the current lost frame and a subframe gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
Optionally, in step 120, the foregoing global gain gradient α may be represented by using an equation (3): $α = 1.0 - delta * scale$
where
delta may represent an adjustment gradient of α, and a value of delta may range from 0.5 to 1;
scale may represent a tuning amplitude of α, which determines a degree at which the current lost frame approaches the previous frame in a current condition, and may range from 0 to 1, where a smaller value may indicate that energy of the current lost frame is closer to that of the previous frame, and a larger value may indicate that the energy of the current lost frame is rather weaker than that of the previous frame.
Optionally, as an embodiment, in step 120, in a case in which the decoder side determines that a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which it is determined that a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, the decoder side may determine that the global gain gradient is 1.
Specifically, in a case in which the decoder side determines that the coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which the decoder side determines that the frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, the global gain of the current lost frame may be the same as the global gain of the previous frame, and therefore, it may be determined that α is 1. For example, for the equation (3), a value of delta may be 0.6, and a value of scale may be 0.
Optionally, as another embodiment, in step 120, in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, the decoder side may determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
Specifically, in a case in which it cannot be determined whether the coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss or whether the frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, the decoder side may determine that α is a relatively small value, that is, α may be less than the preset first threshold. For example, the first threshold may be 0.5. For example, for the equation (3), a value of delta may be 0.65, and a value of scale may be 0.8.
In the foregoing embodiment, the decoder side may determine whether the coding mode of the last frame received before the frame loss is the same as the coding mode of the current lost frame, or determine whether the frame class of the last frame received before the frame loss is the same as the frame class of the current lost frame according to the frame class of the last frame received before the frame loss and/or the quantity of continuously lost frames. For example, if the quantity of continuously lost frames is less than or equal to 3, the decoder side may determine that the coding mode of the last received frame is the same as the coding mode of the current lost frame, or if the quantity of continuously lost frames is greater than 3, the decoder side cannot determine that the coding mode of the last received frame is the same as the coding mode of the current lost frame. For another example, if the last received frame is an onset frame of a voiced frame or an onset frame of an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, the decoder side may determine that the frame class of the current lost frame is the same as the frame class of the last received frame, or if the quantity of continuously lost frames is greater than 3, the decoder side cannot determine whether the coding mode of the last frame received before the frame loss is the same as the coding mode of the current lost frame, or whether the frame class of the last received frame is the same as the frame class of the current lost frame.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, or in a case in which it is determined that the last frame received before the frame loss is an audio frame or a silence frame, the decoder side may determine the global gain gradient, and enable the global gain gradient to be greater than a preset first threshold.
Specifically, if the decoder side determines that the last frame received before the frame loss is an onset frame of a voiced frame, it may be determined that the current lost frame is probably a voiced frame, and accordingly, it may be determined that α is a relatively large value, that is, α may be greater than the preset first threshold. For example, for the equation (3), a value of delta may be 0.5, and a value of scale may be 0.4.
If the decoder side determines that the last frame received before the frame loss is an audio frame or a silence frame, it may be also determined that α is a relatively large value, that is, α may be greater than the preset first threshold. For example, for the equation (3), a value of delta may be 0.5, and a value of scale may be 0.4.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of an unvoiced frame, the decoder side may determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
If the last frame received before the frame loss is an onset frame of an unvoiced frame, the current lost frame may be an unvoiced frame, and accordingly, the decoder side may determine that α is a relatively small value, that is, α may be less than the preset first threshold. For example, for the equation (3), a value of delta may be 0.8, and a value of scale may be 0.65.
In addition, in addition to the cases indicated by the foregoing recovery information, in another case, the decoder side may determine that α is a relatively small value, that is, α may be less than the preset first threshold. For example, for the equation (3), a value of delta may be 0.8, and a value of scale may be 0.75.
Optionally, as another embodiment, a value range of the foregoing first threshold may be as follows: 0 < the first threshold < 1.
Optionally, as another embodiment, the decoder side may determine a subframe gain gradient of the current lost frame according to the recovery information; and determine the subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer.
In addition to that the decoder side may determine the global gain gradient of the current lost frame according to the foregoing recovery information, the decoder side may also determine the subframe gain gradient of the current lost frame according to the foregoing recovery information. For example, the decoder side may weight subframe gains of the previous N frames, and then determine the subframe gain of the current lost frame according to the weighted subframe gains and the subframe gain gradient.
Specifically, a subframe gain SubGain of the current lost frame may be represented by using an equation (4): $SubGain = f (β, SubGain (- n))$
where
SubGain(-n) may represent a subframe gain of the n^th frame in the previous N frames, and β may represent the subframe gain gradient of the current lost frame.
For example, the decoder side may determine a subframe gain SubGain of the current lost frame according to an equation (5): $SubGain = β * \sum_{n = 1}^{N} w_{n} SubGain (- n)$
$\sum_{n - 1}^{N} w_{n} = 1,$
wm may represent a weighted value that corresponds to the n^th frame in the previous N frames, SubGain(-n) may represent a subframe gain of the n^th frame, and β may represent the subframe gain gradient of the current lost frame, where generally, β may range from 1 and 2.
It should be understood that the example of the foregoing equation (5) only aims to help a person skilled in the art better understand this embodiment of the present invention, but is not intended to limit the scope of this embodiment of the present invention. The person skilled in the art may make various equivalent modifications or changes based on the equation (4), to determine various specific representation forms of the equation (4), where these modifications or changes also fall within the scope of the present invention.
To simplify a process, the decoder side may determine the subframe gain of the current lost frame according to a subframe gain of the previous frame of the current lost frame, and the subframe gain gradient.
It can be seen that, in this embodiment, instead of simply setting a subframe gain of a current lost frame to a fixed value, the subframe gain of the current lost frame is determined after a subframe gain gradient is determined according to recovery information, and therefore, a synthesized high frequency band signal is adjusted according to the subframe gain of the current lost frame and a global gain of the current lost frame, so that transition of the high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
Optionally, as another embodiment, in a case in which it cannot be determined whether the coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss or whether the frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, the decoder side may determine the subframe gain gradient, and enable the sub frame gain gradient to be less than or equal to a preset second threshold and greater than 0.
For example, the second threshold may be 1.5, and β may be 1.25.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, the decoder side may determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
If the last frame received before the frame loss is an onset frame of a voiced frame, the current lost frame is probably a voiced frame, and the decoder side may determine that β is a relatively large value, for example, β may be 2.0.
In addition, for β, in addition to the two cases indicated by the foregoing recovery information, β may be 1 in another case.
Optionally, as another embodiment, a value range of the foregoing second threshold is as follows: 1 < the second threshold < 2.
FIG. 2 is a schematic flowchart of a method for processing a lost frame according to another embodiment of the present invention. The method in FIG. 2 is executed by a decoder side.
210: Determine a synthesized high frequency band signal of a current lost frame.
The decoder side may determine the synthesized high frequency band signal of the current lost frame according to the prior art. For example, the decoder side may determine a synthesized high frequency band excitation signal of the current lost frame according to a parameter of a previous frame of the current lost frame. Specifically, the decoder side may use an LPC parameter of the previous frame of the current lost frame as an LPC parameter of the current frame, and may obtain a high frequency band excitation signal by using parameters such as a pitch period, an algebraic codebook, and gains that are obtained by a core-layer decoder of the previous frame. The decoder side may use the high frequency band excitation signal as a high frequency band excitation signal of the current lost frame, and then process the high frequency band excitation signal by using an LPC synthesis filter that is generated by using the LPC parameter, to obtain the synthesized high frequency band signal of the current lost frame.
220: Determine recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame.
For detailed description of the recovery information, refer to the description in the embodiment of FIG. 1, and details are not described herein again.
230: Determine a subframe gain gradient of the current lost frame according to the recovery information.
240: Determine a subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer.
For example, the decoder side may weight subframe gains of the previous N frames, and then determine the subframe gain of the current lost frame according to the weighted subframe gains and the subframe gain gradient.
Specifically, a subframe gain SubGain of the current lost frame may be represented by using the equation (4).
For example, the decoder side may determine a subframe gain SubGain of the current lost frame according to the equation (5).
It should be understood that the example of the foregoing equation (5) only aims to help a person skilled in the art better understand this embodiment of the present invention, but is not intended to limit the scope of this embodiment of the present invention. The person skilled in the art may make various equivalent modifications or changes based on the equation (4), to determine various specific representation forms of the equation (4), where these modifications or changes also fall within the scope of the present invention.
To simplify a process, the decoder side may determine the subframe gain of the current lost frame according to a subframe gain of the previous frame of the current lost frame, and the subframe gain gradient.
250: Adjust the synthesized high frequency band signal of the current lost frame according to the subframe gain of the current lost frame and a global gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
For example, the decoder side may set a fixed global gain gradient according to the prior art, and then determine the global gain of the current lost frame according to the fixed global gain gradient and a global gain of the previous frame.
In the prior art, the decoder side sets the subframe gain of the current lost frame to a fixed value, and adjusts the synthesized high frequency band signal of the current lost frame according to the fixed value and the global gain of the current lost frame, which causes discontinuous transition of the final high frequency band signal before and after the frame loss, and generation of severe noise. However, in this embodiment of the present invention, the decoder side may determine the subframe gain gradient according to the recovery information, and then determine the subframe gain of the current lost frame according to the subframe gain gradient, instead of simply setting the subframe gain of the current lost frame to the fixed value. The recovery information describes a related feature of a frame loss event, and therefore, the subframe gain of the current lost frame is more accurate. Therefore, the decoder side adjusts the synthesized high frequency signal according to the subframe gain, so that transition of the re-established high frequency band signal can be natural and smooth, and noise in the re-established high frequency band signal can be attenuated, thereby improving quality of the re-established high frequency band signal.
In this embodiment, a subframe gain gradient of a current lost frame is determined according to recovery information, a subframe gain of the current lost frame is determined according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the subframe gain of the current lost frame and a global gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
Optionally, as another embodiment, in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, the decoder side may determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
For example, the second threshold may be 1.5, and β may be 1.25.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, the decoder side may determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
If the last frame received before the frame loss is an onset frame of a voiced frame, the current lost frame is probably a voiced frame, and the decoder side may determine that β is a relatively large value, for example, β may be 2.0.
In addition, for β, in addition to the two cases indicated by the foregoing recovery information, β may be 1 in another case.
Optionally, as another embodiment, a value range of the foregoing second threshold may be as follows: 1 < the second threshold < 2.
It can be seen from the foregoing that, a decoder side may determine a global gain of a current lost frame according to this embodiment of the present invention, and determine a subframe gain of the current lost frame according to the prior art; or a decoder side may determine a subframe gain of a current lost frame according to this embodiment of the present invention, and determine a global gain of the current lost frame according to the prior art; or a decoder side may determine a subframe gain of a current lost frame and a global gain of the current lost frame according to this embodiment of the present invention. All of the foregoing methods enable transition of a high frequency band signal of the current lost frame to be natural and smooth, and can attenuate noise in the high frequency band signal, thereby improving quality of the high frequency band signal.
FIG. 3 is a schematic flowchart of a process of a method for processing a lost frame according to an embodiment of the present invention.
301: Parse a frame loss flag in a received bitstream.
This process may be executed according to the prior art.
302: Determine whether a current frame is lost according to the frame loss flag.
If the frame loss flag indicates that the current frame is not lost, step 303 is executed.
If the frame loss flag indicates that the current frame is lost, steps 304 to 306 are executed.
303: If the frame loss flag indicates that the current frame is not lost, decode the bitstream, and recover the current frame.
If the frame loss flag indicates that the current frame is lost, steps 304 to 306 may be executed simultaneously, or steps 304 to 306 are executed in a specific sequence, which is not limited in this embodiment of the present invention.
304: Determine a synthesized high frequency band signal of a current lost frame.
For example, the decoder side may determine a synthesized high frequency band excitation signal of the current lost frame according to a parameter of a previous frame of the current lost frame. Specifically, the decoder side may use an LPC parameter of the previous frame of the current lost frame as an LPC parameter of the current frame, and may obtain a high frequency band excitation signal by using parameters such as a pitch period, an algebraic codebook, and gains that are obtained by a core-layer decoder of the previous frame. The decoder side may use the high frequency band excitation signal as a high frequency band excitation signal of the current lost frame, and then process the high frequency band excitation signal by using an LPC synthesis filter that is generated by using the LPC parameter, to obtain the synthesized high frequency band signal of the current lost frame.
305: Determine a global gain of the current lost frame.
Optionally, the decoder side may determine a global gain gradient of the current lost frame according to recovery information of the current lost frame, where the recovery information may include at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames; and then determine the global gain of the current lost frame according to the global gain gradient of the current lost frame and a global gain of each frame in previous M frames.
For example, optionally, the decoder side may further determine the global gain of the current lost frame according to the prior art. For example, the global gain of the current lost frame may be obtained by multiplying a global gain of the previous frame by a fixed global gain gradient.
306: Determine a subframe gain of the current lost frame.
Optionally, the decoder side may also determine a subframe gain gradient of the current lost frame according to the recovery information of the current lost frame, and then determine the subframe gain of the current lost frame according to the global gain gradient of the current lost frame and a subframe gain of each frame in previous N frames.
Optionally, the decoder side may determine the subframe gain of the current lost frame according to the prior art, for example, set the subframe gain of the current lost frame to a fixed value.
It should be understood that, to improve quality of a re-established high frequency band signal that corresponds to the current lost frame, if the global gain of the current lost frame is determined in step 305 according to the prior art, in step 306, the subframe gain of the current lost frame needs to be determined according to the method in the embodiment of FIG. 2. If the global gain of the current lost frame is determined in step 305 by using the method in the embodiment of FIG. 1, in step 306, the subframe gain of the current lost frame may be determined by using the method in the embodiment of FIG. 2, or the subframe gain of the current lost frame may be determined according to the prior art.
307: Adjust, according to the global gain of the current lost frame that is obtained in step 305 and the subframe gain of the current lost frame that is obtained in step 306, the synthesized high frequency band signal obtained in step 304, to obtain a high frequency band signal of the current lost frame.
In this embodiment of the present invention, a global gain gradient of a current lost frame is determined according to recovery information or a subframe gain gradient of a current lost frame is determined according to recovery information, to obtain a global gain of the current lost frame and a subframe gain of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the global gain of the current lost frame and the subframe gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
FIG. 4 is a schematic block diagram of a decoder according to an embodiment of the present invention. An example of a device 400 in FIG. 4 is the decoder. The device 400 includes a first determining unit 410, a second determining unit 420, a third determining unit 430, a fourth determining unit 440, and an adjusting unit 450.
The first determining unit 410 determines a synthesized high frequency band signal of a current lost frame. The second determining unit 420 determines recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame. The third determining unit 430 determines a global gain gradient of the current lost frame according to the recovery information. The fourth determining unit 440 determines a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, where M is a positive integer. A subframe gain of the current lost frame is determined. The adjusting unit 450 adjusts the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and the subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
In this embodiment of the present invention, a global gain gradient of a current lost frame is determined according to recovery information, a global gain of the current lost frame is determined according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the global gain of the current lost frame and a subframe gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
Optionally, as an embodiment, in a case in which it is determined that a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which it is determined that a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, the third determining unit 430 may determine that the global gain gradient is 1.
Optionally, as another embodiment, in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, the third determining unit 430 may determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, or in a case in which it is determined that the last frame received before the frame loss is an audio frame or a silence frame, the third determining unit 430 may determine the global gain gradient, and enable the global gain gradient to be greater than a preset first threshold.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of an unvoiced frame, the third determining unit 430 may determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
Optionally, as another embodiment, a fifth determining unit 450 is further included. The fifth determining unit 450 may determine a subframe gain gradient of the current lost frame according to the recovery information. The fifth determining unit 450 may determine the subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer.
Optionally, as another embodiment, in a case in which it cannot be determined whether the coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, the fifth determining unit 450 may determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, the fifth determining unit 450 may determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
For other functions and operations of the device 400, refer to the processes in the method embodiments in FIG. 1 and FIG. 3, and details are not described herein again to avoid repetition.
FIG. 5 is a schematic block diagram of a decoder according to another embodiment of the present invention. An example of a device 500 in FIG. 5 is the decoder. The device 500 in FIG. 5 includes a first determining unit 510, a second determining unit 520, a third determining unit 530, a fourth determining unit 540, and an adjusting unit 550.
The first determining unit 510 determines a synthesized high frequency band signal of a current lost frame. The second determining unit 520 determines recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame. The third determining unit 530 determines a subframe gain gradient of the current lost frame according to the recovery information. The fourth determining unit 540 determines a subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer. The adjusting unit 550 adjusts the synthesized high frequency band signal of the current lost frame according to the subframe gain of the current lost frame and a global gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
In this embodiment, a subframe gain gradient of a current lost frame is determined according to recovery information, a subframe gain of the current lost frame is determined according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the subframe gain of the current lost frame and a global gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
Optionally, as an embodiment, in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, the third determining unit 530 may determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, the third determining unit 530 may determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
For other functions and operations of the device 500, refer to the processes in the method embodiments in FIG. 2 and FIG. 3, and details are not described herein again to avoid repetition.
FIG. 6 is a schematic block diagram of a decoder according to an embodiment of the present invention. An example of a device 600 in FIG. 6 is the decoder. The device 600 includes a memory 610 and a processor 620.
The memory 610 may include a random access memory, a flash memory, a read-only memory, a programmable read-only memory, a non-volatile memory, a register, or the like. The processor 620 may be a central processing unit (Central Processing Unit, CPU).
The memory 610 is configured to store an executable instruction. The processor 620 may execute the executable instruction stored in the memory 610, and is configured to: determine a synthesized high frequency band signal of a current lost frame; determine recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame; determine a global gain gradient of the current lost frame according to the recovery information; determine a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, where M is a positive integer; and adjust the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and a subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
In this embodiment of the present invention, a global gain gradient of a current lost frame is determined according to recovery information, a global gain of the current lost frame is determined according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the global gain of the current lost frame and a subframe gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
Optionally, as an embodiment, in a case in which it is determined that a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which it is determined that a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, the processor 620 may determine that the global gain gradient is 1.
Optionally, as another embodiment, in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, the processor 620 may determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, or in a case in which it is determined that the last frame received before the frame loss is an audio frame or a silence frame, the processor 620 may determine the global gain gradient, and enable the global gain gradient to be greater than a preset first threshold.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, the processor 620 may determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
Optionally, as another embodiment, the processor 620 may determine a subframe gain gradient of the current lost frame according to the recovery information; and determine the subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer.
Optionally, as another embodiment, in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, the processor 620 may determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, the processor 620 may determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
For other functions and operations of the device 600, refer to the processes in the method embodiments in FIG. 1 and FIG. 3, and details are not described herein again to avoid repetition.
FIG. 7 is a schematic block diagram of a decoder according to another embodiment of the present invention. An example of a device 700 in FIG. 7 is the decoder. The device 700 in FIG. 7 includes a memory 710 and a processor 720.
The memory 710 may include a random access memory, a flash memory, a read-only memory, a programmable read-only memory, a non-volatile memory, a register, or the like. The processor 720 may be a central processing unit (Central Processing Unit, CPU).
The memory 710 is configured to store an executable instruction. The processor 720 may execute the executable instruction stored in the memory 710, and is configured to: determine a synthesized high frequency band signal of a current lost frame; determine recovery information that corresponds to the current lost frame, where the recovery information includes at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, where the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame; determine a subframe gain gradient of the current lost frame according to the recovery information; determine a subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, where N is a positive integer; and adjust the synthesized high frequency band signal of the current lost frame according to the subframe gain of the current lost frame and a global gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
In this embodiment, a subframe gain gradient of a current lost frame is determined according to recovery information, a subframe gain of the current lost frame is determined according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, and a synthesized high frequency band signal of the current lost frame is adjusted according to the subframe gain of the current lost frame and a global gain of the current lost frame, so that transition of a high frequency band signal of the current lost frame can be natural and smooth, and noise in the high frequency band signal can be attenuated, thereby improving quality of the high frequency band signal.
Optionally, as an embodiment, in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, the processor 720 may determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
Optionally, as another embodiment, in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, the processor 720 may determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
For other functions and operations of the device 700, refer to the processes in the method embodiments in FIG. 2 and FIG. 3, and details are not described herein again to avoid repetition.
A person of ordinary skill in the art may be aware that, in combination with the examples described in the embodiments disclosed in this specification, units and algorithm steps may be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed by hardware or software depends on particular applications and design constraint conditions of the technical solutions. A person skilled in the art may use different methods to implement the described functions for each particular application, but it should not be considered that the implementation goes beyond the scope of the present invention.
It may be clearly understood by a person skilled in the art that, for the purpose of convenient and brief description, for a detailed working process of the foregoing system, apparatus, and unit, refer to a corresponding process in the foregoing method embodiments, and details are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described apparatus embodiment is merely exemplary. For example, the unit division is merely logical function division and may be other division in actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.
When the functions are implemented in the form of a software functional unit and sold or used as an independent product, the functions may be stored in a computer-readable storage medium. Based on such an understanding, the technical solutions of the present invention essentially, or the part contributing to the prior art, or some of the technical solutions may be implemented in a form of a software product. The computer software product is stored in a storage medium, and includes several instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to perform all or some of the steps of the methods described in the embodiments of the present invention. The foregoing storage medium includes: any medium that can store program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk, or an optical disc.
The foregoing descriptions are merely specific implementation manners of the present invention, but are not intended to limit the protection scope of the present invention. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

A method for processing a lost frame, comprising:
determining a synthesized high frequency band signal of a current lost frame;

determining recovery information that corresponds to the current lost frame, wherein the recovery information comprises at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, wherein the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame;

determining a global gain gradient of the current lost frame according to the recovery information;

determining a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, wherein M is a positive integer; and

adjusting the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and a subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
The method according to claim 1, wherein the determining a global gain gradient of the current lost frame according to the recovery information comprises:
in a case in which it is determined that a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which it is determined that a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, determining that the global gain gradient is 1.
The method according to claim 1, wherein the determining a global gain gradient of the current lost frame according to the recovery information comprises:
in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, determining the global gain gradient, and enabling the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
The method according to claim 1, wherein the determining a global gain gradient of the current lost frame according to the recovery information comprises:
in a case in which the last frame received before the frame loss is an onset frame of a voiced frame, or in a case in which it is determined that the last frame received before the frame loss is an audio frame or a silence frame, determining the global gain gradient, and enabling the global gain gradient to be greater than a preset first threshold.
The method according to claim 1, wherein the determining a global gain gradient of the current lost frame according to the recovery information comprises:
in a case in which the last frame received before the frame loss is an onset frame of an unvoiced frame, determining the global gain gradient, and enabling the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
The method according to any one of claims 1 to 5, further comprising:
determining a subframe gain gradient of the current lost frame according to the recovery information; and determining the subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, wherein N is a positive integer.
The method according to claim 6, wherein the determining a subframe gain gradient of the current lost frame according to the recovery information comprises:
in a case in which it cannot be determined whether the coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss or whether the frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determining the subframe gain gradient, and enabling the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
The method according to claim 6, wherein the determining a subframe gain gradient of the current lost frame according to the recovery information comprises:
in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, determining the subframe gain gradient, and enabling the subframe gain gradient to be greater than a preset second threshold.
A method for processing a lost frame, comprising:
determining a synthesized high frequency band signal of a current lost frame;

determining recovery information that corresponds to the current lost frame, wherein the recovery information comprises at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, wherein the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame;

determining a subframe gain gradient of the current lost frame according to the recovery information;

determining a subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, wherein N is a positive integer;

determining a global gain of the current lost frame; and

adjusting the synthesized high frequency band signal of the current lost frame according to the subframe gain of the current lost frame and the global gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
The method according to claim 9, wherein the determining a subframe gain gradient of the current lost frame according to the recovery information comprises:
in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determining the subframe gain gradient, and enabling the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
The method according to claim 9, wherein the determining a subframe gain gradient of the current lost frame according to the recovery information comprises:
in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, determining the subframe gain gradient, and enabling the subframe gain gradient to be greater than a preset second threshold.
A decoder, comprising:
a first determining unit, configured to determine a synthesized high frequency band signal of a current lost frame;

a second determining unit, configured to determine recovery information that corresponds to the current lost frame, wherein the recovery information comprises at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, wherein the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame;

a third determining unit, configured to determine a global gain gradient of the current lost frame according to the recovery information;

a fourth determining unit, configured to determine a global gain of the current lost frame according to the global gain gradient and a global gain of each frame in previous M frames of the current lost frame, wherein M is a positive integer; and

an adjusting unit, configured to adjust the synthesized high frequency band signal of the current lost frame according to the global gain of the current lost frame and a subframe gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
The decoder according to claim 12, wherein the second determining unit is specifically configured to: in a case in which it is determined that a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, or in a case in which it is determined that a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, and the quantity of continuously lost frames is less than or equal to 3, determine that the global gain gradient is 1.
The decoder according to claim 12, wherein the second determining unit is specifically configured to: in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame or a voiced frame, and the quantity of continuously lost frames is less than or equal to 3, determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
The decoder according to claim 12, wherein the second determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, or in a case in which it is determined that the last frame received before the frame loss is an audio frame or a silence frame, determine the global gain gradient, and enable the global gain gradient to be greater than a preset first threshold.
The decoder according to claim 12, wherein the second determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of an unvoiced frame, determine the global gain gradient, and enable the global gain gradient to be less than or equal to a preset first threshold and greater than 0.
The decoder according to any one of claims 12 to 16, further comprising:
a fifth determining unit, configured to determine a subframe gain gradient of the current lost frame according to the recovery information, and determine the subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, wherein N is a positive integer.
The decoder according to claim 17, wherein the fifth determining unit is specifically configured to: in a case in which it cannot be determined whether the coding mode of the current lost frame is the same as the coding mode of the last frame received before the frame loss or whether the frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
The decoder according to claim 17, wherein the fifth determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of an unvoiced frame, determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.
A decoder, comprising:
a first determining unit, configured to determine a synthesized high frequency band signal of a current lost frame;

a second determining unit, configured to determine recovery information that corresponds to the current lost frame, wherein the recovery information comprises at least one of the following: a coding mode before frame loss, a frame class of a last frame received before the frame loss, and a quantity of continuously lost frames, wherein the quantity of continuously lost frames is a quantity of frames that are continuously lost until the current lost frame;

a third determining unit, configured to determine a subframe gain gradient of the current lost frame according to the recovery information;

a fourth determining unit, configured to determine a subframe gain of the current lost frame according to the subframe gain gradient and a subframe gain of each frame in previous N frames of the current lost frame, wherein N is a positive integer; and

an adjusting unit, configured to adjust the synthesized high frequency band signal of the current lost frame according to the subframe gain of the current lost frame and a global gain of the current lost frame, to obtain a high frequency band signal of the current lost frame.
The decoder according to claim 20, wherein the second determining unit is specifically configured to: in a case in which it cannot be determined whether a coding mode of the current lost frame is the same as a coding mode of the last frame received before the frame loss or whether a frame class of the current lost frame is the same as the frame class of the last frame received before the frame loss, if it is determined that the last frame received before the frame loss is an unvoiced frame, and the quantity of continuously lost frames is less than or equal to 3, determine the subframe gain gradient, and enable the subframe gain gradient to be less than or equal to a preset second threshold and greater than 0.
The decoder according to claim 20, wherein the second determining unit is specifically configured to: in a case in which it is determined that the last frame received before the frame loss is an onset frame of a voiced frame, determine the subframe gain gradient, and enable the subframe gain gradient to be greater than a preset second threshold.